Giant knotweed, Sakhalin knotweed	Status LU: established. 1st record: LU & ITW 1959.
	Sachalin-Knuetkraut	Status Eur.: established. 1st record: UK 1860s.
	Renouée de Sakhaline	RA: ISEIA: B1 – Watch List. Harmonia+: 0,59.
	Sachalin-Staudenknöterich, Riesen-Knöterich	Wikipedia: | Wikispecies: | CABI
	Sachalinse duizendknoop	Back to the list of neophytes

Report the species

→ Report Fallopia sachalinensis to the National Museum of Natural History.

Brief description

Like other Asiatic knotweeds, Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr. colonises a wide range of environments, with a predilection for moist and nitrogen-rich soils. It prefers sunny places or semi-shaded habitats. This pioneer plant proliferates both in ruderal and semi-natural habitats, including riparian areas and open forests. Stem and rhizomes may easily split into small pieces; fragments are able to regenerate a plant, provided a node is present. Giant knotweed produces a small number of viable seeds, but seedlings are seldom observed in the wild. Transport of garden waste and soil contaminated with rhizomes are the major dispersal modes. Where the plant is widely consolidated on river banks it is also spread by floods and can easily colonise downstream.

Fallopia sachalinensis is able to monopolise space and to form dense and persistent populations. It can outcompete most of native herbaceous plant species thanks to early seasonal development, high growth rate and productivity, abundant leaf cover, allelochemical production and clonal spread associated with an extraordinarily high rate of proliferation of below-ground organs. It can even outcompete Fallopia japonica on alluvial riverbanks. Its development reduces plant and invertebrate species diversity, alters habitats for fish and wildlife, change light and energy conditions of the ecosystem, and favours river bank erosion during the winter. It can also break through tarmac and thin layers of concrete, and can penetrate some flood defences (Branquart et al. 2011).

Status and distribution in Luxembourg

Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr. was first documented on 14th May 1959 in Lëtschet (Municipality of Steinsel) by Léopold Reichling (1921-2009) (MNHNL 2000-).

108 records of this melliferous species are listed in the MNHNL-mdata online portal (MNHNL, iNaturalist & GBIF 2019).

Giant knotweed is less common and less widespread in Luxembourg than its relatives Bohemian knotweed (Fallopia ×bohemica), and Japanese knotweed (Fallopia japonica). It sometimes builds huge colonies along riparian ecosystems, as can be seen along the river Alzette in Luxembourg City (beside the Neumünster Abbey in the Grund district) and along the Sûre east of Diekirch. It is mostly found as an ornamental plant in private gardens. Populations in the wild are the result of people fly-tipping their knotweed clippings.

Sometimes grown for ornamental purposes in parks. Naturalised here and there: rare. The frequency of male-sterile and male-fertile colonies, distinguishable by the morphology of the inflorescence, should be specified (Lambinon & Verloove 2012: 193).

Risk assessment

ISEIA protocol

B1 (2+2+3+3) = Watch List (Ries et al. 2013: 18).

Harmonia+ protocol

Overall risk score 0,59 = (Overall Invasion score 0,84 x Overall Impact score 0,70) (Ries et al. 2020).

Worldwide distribution

Bibliography

• Albers, M., S. Kohn, J. Steng & M. Pfeiffenschneider, 2001. – Problematik der Bioinvasion. Kartierung von Japan-Knöterich, Riesenbärenklau und Indischem Springkraut an Woltz, Clerve und Wiltz. Ergebnisse der Kartierung. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, arrondissement nord. August 2001. 7S. + Anhang.
• Bailey, J.P. & A.P. Conolly, 2000. Prize-winners to pariahs – A history of Japanese Knotweed s.l. (Polygonaceae) in the British Isles. Watsonia. 23: 93–110.[PDF]
• Branquart, E., S. Vanderhoeven, W. Van Landuyt, F. Van Rossum, F. Verloove & A. Vervoort, 2011. Harmonia database: Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr. Harmonia version 1.2, Belgian Forum on Invasive Species. URL: http://ias.biodiversity.be [accessed on 2019-10-11]
• CABI, 2019. Fallopia sachalinensis. In: Invasive Species Compendium. Wallingford, UK: CAB International. URL: www.cabi.org/isc [accessed 2020-03-02]
• Glesener, B., M. Pfeiffenschneider & C. Ries, 2009. Die Verbreitung von Impatiens glandulifera, Fallopia japonica, F. sachalinensis, F. ×bohemica und Heracleum mantegazzianum entlang der Hauptfließgewässer Luxemburgs. Bull. Soc. Nat. luxemb. 110 : 69-73. (pdf)
• Lambinon J. & F. Verloove, 2012. Nouvelle flore de la Belgique, du grand-duché de Luxembourg, du Nord de la France et des régions voisines. Sixième édition. Avec la collaboration de L. Delvosalle, B. Toussaint, D. Geerinck, I. Hoste, F. Van Rossum, B. Cornier, R. Schumacker, A. Vanderpoorten et H. Vannerom. Jardin botanique national de Belgique, Meise. CXXXIX + 1195 pp. ISBN : 9789072619884.
• MNHNL, 2000-. Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr. in Recorder-Lux, database on the natural heritage of the Grand Duchy of Luxembourg. Musée national d’histoire naturelle, Luxembourg. URL: https://mdata.mnhn.lu [Accessed 2019-10-11]
• MNHNL, iNaturalist & GBIF, 2019. Fallopia sachalinensis (F. Schmidt Petrop.) Ronse Decr. in MNHNL-mdata, online portal combining species observation from Recorder-Lux, iNaturalist and GBIF. National Museum of Natural History, Luxembourg. URL: https://mdata.mnhn.lu [Accessed 2019-10-11]
• Pfeiffenschneider, M., 2001. – Problematik der Bioinvasion. Nationales Inventar von Riesenbärenklau, Indischem Springkraut und exotischen Knötericharten. Ergebnisse einer Umfrage und Konzept zur Bekämpfung der Riesenbärenklaubestände. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, Service de la conservation de la nature, November 2001. 23 S. + Anhang, Luxembourg.
• Pfeiffenschneider, M., 2007. Über die Verbreitung von Heracleum mantegazzianum, Impatiens glandulifera, Fallopia japonica und F. sachali­nensis entlang der Gewässer Obersauer, Woltz, Clerve, Wiltz und ihrer Nebengewässer (Luxemburg). Bull. Soc. Nat. luxemb. 108 : 7-10. (pdf)
• Pfeiffenschneider, M., 2008. Neophyten in Luxemburg – Projekt Bioinvasion 2007. Arbeitsbericht. 18 S. (pdf)
• Pfeiffenschneider, M. & M. Owaller, 2000. – Kartierung von Japan-Knöterich, Riesenbärenklau und Indischem Springkraut an der Obersauer. Theoretische Grundlagen und Ergebnisse der Kartierung. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, acrrondissement nord. August 2000. 37S. + Anhang, Luxembourg.
• Ries, C. & Y. Krippel, 2021. First records of 56 invasive alien vascular plants in Luxembourg. Bulletin de la Société des naturalistes luxembourgeois 123: 115-127. [PDF 241 KB]
• Ries, C., Y. Krippel & M. Pfeiffenschneider, 2020. Risk assessment after the Harmonia+ protocol of invasive alien vascular plant species in Luxembourg. Bull. Soc. Nat. luxemb. 122: 197-205. [PDF 132 KB]
• Ries, C., Y. Krippel, M. Pfeiffenschneider & S. Schneider, 2013. Environmental impact assessment and black, watch and alert list classification after the ISEIA Protocol of non-native vascular plant species in Luxembourg. Bull. Soc. Nat. luxemb. 114: 15-21. [PDF 652 KB]